1. Field of the Invention
The present invention relates to a back illumination type (back illuminated) solid-state imaging device receiving light from an opposite side to a surface formed with a pixel circuit, a method of producing the same, and a camera including the same.
2. Description of the Related Art
There is known, for example, front illumination type (front illuminated) solid-state imaging devices in which a light receiving unit and a read out transistor are placed within a pixel, so, in a CCD type solid-state imaging device and a CMOS type solid-state imaging device, an area for the light receiving unit is restricted. For an enlargement of the area for the light receiving unit, in the CCD or CMOS type solid-state imaging device, an on-chip lens or a multilayered light receiving unit using photoconductive film has been employed. Also, in the CCD type solid-state imaging device, a frame transfer CCD using a transparent electrode or a thin polysilicon electrode has been employed.
In the above configurations, an effective aperture area of the light receiving unit is enlarged to improve light sensitivity. As a pixel is smaller, an eclipse of incidence light is obviously by a pixel interconnection and a transfer gate electrode unit. Therefore, a back illuminated (back illumination type) solid-state imaging device has been expected as a configuration for high-sensitivity of the light receiving unit. As the back illuminated solid-state imaging device, a CCD type is disclosed by Japanese Unexamined Patent Publication (Kokai) No. 2002-151673, and a MOS type is disclosed by Japanese Unexamined Patent Publication (Kokai) No. 2003-31785. In the back illuminated solid-state imaging device, a frame transfer (FT) type or a frame interline transfer (FIT) type has been employed.
In the case of the CCD type and the MOS type, a p-type silicon substrate is used as a substrate. For example, Japanese Unexamined Patent Publication (Kokai) No. 6-350068 discloses the following three structures for suppressing a dark current at an interface of a back surface, namely, a light incident surface.
A first structure is formed with a p+-layer with a high concentration at the back surface to suppress a depletion at the back surface. A second structure is formed with a transparence electrode via an insulation film at the back surface. A negative voltage is supplied to the transparent electrode to make a hole storage state in the back surface of a substrate. A third structure is injected with negative charges at an insulation film formed at the back surface of the substrate to make the hole storage state in the back surface of the substrate due to the negative charge.